linux-kernel - Re: [PATCH] x86/efistub: Omit physical KASLR when memory reservations exist

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Message-ID: <CAMj1kXEAqKTaXD8o3bM=1u3COG=CYUp7P83L6segM4dKYoDszg@mail.gmail.com>
Date: Thu, 16 May 2024 20:47:27 +0200
From: Ard Biesheuvel <ardb@...nel.org>
To: Kees Cook <keescook@...omium.org>
Cc: "Chaney, Ben" <bchaney@...mai.com>, Ard Biesheuvel <ardb+git@...gle.com>, 
	"linux-efi@...r.kernel.org" <linux-efi@...r.kernel.org>, 
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "x86@...nel.org" <x86@...nel.org>, 
	"stable@...r.kernel.org" <stable@...r.kernel.org>
Subject: Re: [PATCH] x86/efistub: Omit physical KASLR when memory reservations exist

On Thu, 16 May 2024 at 20:45, Kees Cook <keescook@...omium.org> wrote:
>
> On Thu, May 16, 2024 at 05:29:11PM +0000, Chaney, Ben wrote:
> > > +static efi_status_t parse_options(const char *cmdline)
> > > +{
> > > + static const char opts[][14] = {
> > > + "mem=", "memmap=", "efi_fake_mem=", "hugepages="
> > > + };
> > > +
> >
> > I think we probably want to include both crashkernel and pstore as arguments that can disable this randomization.
>
> The carve-outs that pstore uses should already appear in the physical
> memory mapping that EFI has. (i.e. those things get listed in e820 as
> non-RAM, etc)
>
> I don't know anything about crashkernel, but if we really do have a lot
> of these, we likely need to find a way to express them to EFI...
>

Perhaps. But the fact that the current KASLR code ignores it entirely
suggests that this has not been a problem up to this point.